Articular cartilage is a unique tissue both in structure and function. Almost 70% of the dry weight of this tissue can be accounted for by collagen. This collagen differs from other mammalian collagens studied in that it is composed of 3 identical alpha-chains. It is extremely rich in OH-lysine residues and O-glycosidically bound carbohydrate. More recently it was shown that osteoarthritic cartilage synthesizes in addition to its tissue characteristic collagen, a collagen of the "skin type" containing alpha 2 chains. Lysosomal enzymes seem to be associated with this change in metabolic behavior. In the proposed experiments, we plan to: a) characterize chemically the collagen from normal and osteoarthritic cartilage of various ages. b) Study the behavior of these tissues in organ and cell culture, primarily in relationship to the synthesis of collagen. c) Investigate the rates of turnover of this collagen "in vivo" and "in vitro" in various animal models. d) Investigate the enzymatic susceptibility of these tissues. e) Effect of enzymes on this collagen. f) Role of the OH-lysine residues in glycosylation and crosslinking. The studies in question involve the use of chondrocytes in culture, cartilage explants, and the investigation of various environmental factors (media, pH, enzymes, metabolic inhibitors, etc.) that may affect the metabolic behavior of these systems.